|The ecological impact of beach nourishment and the restrained habitat of key species: experimental insights and field data|
Speybroeck, J.; Hendrickx, F.; Degraer, S.; Vincx, M. (2007). The ecological impact of beach nourishment and the restrained habitat of key species: experimental insights and field data, in: Speybroeck, J. (2007). Ecologie van macrobenthos als een basis voor een ecologische bijsturing van strandsuppleties = Ecology of macrobenthos as a baseline for an ecological adjustment of beach nourishment. pp. 109-123
In: Speybroeck, J. (2007). Ecologie van macrobenthos als een basis voor een ecologische bijsturing van strandsuppleties = Ecology of macrobenthos as a baseline for an ecological adjustment of beach nourishment. PhD Thesis. Universiteit Gent. Vakgroep Biologie, sectie Mariene Biologie: Gent. 189 pp., more
Beach nourishment; Grain size; Habitat; Sandy beaches; Polychaeta [WoRMS]; Scolelepis squamata (Müller, 1806) [WoRMS]; ANE, Belgium [gazetteer]; Marine
Nowadays, beach nourishment is widely considered as a better alternative than the construction of hard structures to protect a coast against detrimental erosive effects, both from an ecological as from an engineering perspective. Most studies conducted on the ecological impact of beach nourishment are short-term, post hoc monitoring investigations of the benthic macrofauna. Little is known of the ruling biological processes during and after nourishment. To allow recolonisation after nourishment, habitat demands will have to match the characteristics of the nourished beach. The benthic habitat of the intertidal key polychaete Scolelepis squamata was investigated through lab experiments and field data analysis, aiming at guidelines for impact mitigation of beach nourishment. Survival, feeding frequency, burrowing time and grain size selection were investigated to assess tolerance and preference for sediment types varying in median grain size. Remarkable preference for very coarse sands contrasted with longer burrowing time. Feeding frequency was higher in coarser sands. Survival was total in all but very fine sands, where total mortality was observed. Data from five beaches were used to model Scolelepis abundance based on three environmental variables (elevation, median grain size and slope). Slope did not contribute significantly to any model. The selected model used median grain size, elevation and a second degree term of the latter. The degree of overdispersion remained large across models. Experimentally observed grain size preference seems to conflict with in situ distribution. High levels of overdispersion in our field data analysis suggest other additional factors (additional physical variables, interspecific and intraspecific interactions) determine Scolelepis abundance and post-nourishment recovery. For swift recolonisation of nourished beaches, we advocate nourishment to be executed in winter by means of foreshore nourishment in sections with alternation of nourished and unnourished stretches of beach. Concerning the fill quality, very fine sands and high concentrations of fines should be avoided, while also very coarse sands may hamper Scolelepis squamata populations. Factors explaining cross-shore and long-shore distribution of the species are still poorly known, as apparent from our field data analysis.